13. 変換?逆変換する方法
? RFC3492
Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications (IDNA)
http://tools.ietf.org/html/rfc3492
? libidn - GNU IDN Library
C/C++/C#/Java API/Emacs API
http://www.gnu.org/software/libidn/